Question

In drinking water, if the maximum prescribed concentration of copper is x mg dm⁻³, the maximum prescribed concentration of zinc will be

• A. 15/x
• B. x/15
• C. 6/10 x
• D. 5/6 x
• E. None of these

Hint:

For questions based on factual data like permissible limits, it's helpful to remember a few key values. For drinking water, typical values are: Fluoride (~1.5 ppm), Lead (~0.01 ppm), Copper (~1.5 ppm), Zinc (~15 ppm). If a question presents strange relationships between these values, it is highly likely to be flawed.

Answer 1

Answer: (E)

Step 1: Understanding the Concept:
This question relates to environmental chemistry and the standard permissible limits of metal ions in drinking water as set by health organizations like the WHO or national bodies like the Bureau of Indian Standards (BIS).
Step 2: Analyzing Standard Data:
According to the Bureau of Indian Standards (BIS:10500) and WHO guidelines for drinking water quality: - The maximum permissible limit for Copper (Cu) is typically around 1.5 mg/L (or 1.5 mg dm⁻³). - The maximum permissible limit for Zinc (Zn) is typically around 15 mg/L (or 15 mg dm⁻³). Let's assume the variable `x` in the question refers to the maximum prescribed concentration of copper. So, \(x \approx 1.5\) mg dm⁻³. The maximum prescribed concentration of zinc is \( \approx 15\) mg dm⁻³. Step 3: Evaluating the Options based on Standard Data:
The question asks for the concentration of zinc. The actual value is approximately 15 mg dm⁻³. The value of x is approximately 1.5 mg dm⁻³. Let's check the options: (A) \(15/x = 15/1.5 = 10\). The required zinc concentration is 15. So this is incorrect. (B) \(x/15 = 1.5/15 = 0.1\). Incorrect. (C) \((6/10)x = 0.6 \times 1.5 = 0.9\). Incorrect. (D) \((5/6)x \approx 0.83 \times 1.5 \approx 1.25\). Incorrect. None of the options logically connect the standard limits of copper and zinc. The ratio of the permissible limits is Zn/Cu = 15/1.5 = 10. The options provided are nonsensical fractions. Therefore, the question is considered erroneous. No logical solution can be derived.
Step 4: Final Answer:
Based on standard water quality guidelines, none of the provided options are correct. The question is ill-posed or contains significant errors.